Abstract

Double-quantum-filtered NMR and inversion-recovery spectroscopy were employed to exploit the temperature-dependent dynamics of confined in MCM-41. Samples with three pore sizes of 1.58, 2.03, and and two contents were investigated. The reorientation correlation times of confined in variously sized pores exhibit different temperature dependencies. The results reveal that the molecules at fast motion site remain mobile below and a liquid-liquid phase transition occurs around this temperature for all samples studied. This temperature is thought to be unreachable for supercooled . Particularly, in loaded samples with pore diameters of 1.58 and , the reorientational correlation times of at fast motion site exhibit Arrhenius behavior between 225 and , while other samples show power law dependency. Thus, a liquid phase of the fragile type in bigger pores changes to the strong type in samples with smaller pores.

Received 30 September 2005Accepted 01 December 2006Published online 23 January 2007

Acknowledgments:

The authors would like to thank the National Science Council of the Republic of China, Taiwan, for financially supporting this research under Contract Nos. NSC 92-2113-M-001-038, NSC 93-2113-M-001-047, and NSC 94-2113-M-001-021.